Levothyroxine Intervention in Pregnant Women with TSH （2.5 MIU/L-upper Limit of Reference Range） and Negative Thyroid Peroxidase Antibody

The goal of this clinical trial is to learn if levothyroxine (L-T4) works to treat pregnant women with TSH 2.5 mIU/L-the upper limit of reference range (ULRR) of pregnancy and TPOAb-negative. It will also learn about the safety of L-T4. The main quesitons the investigator want to answer are: * Will L-T4 reduce miscarriage rates and have an impact on pregnancy complications in pregnant participants? * What medical issues do participants have when taking L-T4 during pregnancy? -Investigators will compare L-T4 with placebo (a substance with a similar appearance without medication) to see if L-T4 could reduce miscarriage rates Participants should: * Take L-T4 or placebo during the whole pregnancy. * Visit the hospital once every 6-8 weeks during pregnancy for checkups and tests * Keep a diary of their pregncny complications and daily record of L-T4 or placebo intake. * Visit the hospital for examination 42 days postpartum for checkups and follow up by phone at 6 and 12 months postpartum.

NCT Number	NCT06653907
Lead Sponsor	Yang ZHANG Collaborators: National Research Institute for Family Planning, China, The Fourth Hospital of Shijiazhuang
Conditions	Thyroid Abnormalities, Pregnant Woman, Pregnancy Outcomes
Enrollment	400 participants
Start Date	2024-10-25
Primary Completion	2026-12-31 (estimated)
Study Completion	2027-10-31 (estimated)
Updated on ClinicalTrials.gov	2024-10-23